The reaction of isocyanates with amines is known in the art and is an extremely fast reaction. It has only been recently that higher molecular weight diamines could be made to react with diisocyanates in a controlled fashion. Work in this area led to the Reaction Injection Molding (RIM) process for the preparation of polyurea plastics.
In U. S. Pat. No. 4,490,520, Orgasa et al. disclose a process for the preparation of a polyamide with improved properties which comprises polymerizing an .omega.-lactam in contact with (1) an alkalai catalyst and (2) a product obtained by the reaction between (a) a polyisocyanate (b) a polyoxyalkylene amine.
Kwong U.S. Pat. No.3,257,342 is directed to epoxy resins that are cured with a amidoamine prepared by reacting about two molar equivalents of a polyoxyalkylene-diamine with an aliphatic dicarboxylic acid at high temperature. These products are amide-linked diamines in contrast to urea-linked diamines in this instant invention. The application of amidoamine in epoxy/polyamide coatings is described by V. Brytus in the Journal of Coatings Technology, Vol. 58, No. 740, Sept. 1986 pp: 45-49.
In contrast to polyamide and polyurethane reactions, the formation of urea-linkages from isocyanates and amines is an extremely fast reaction. In general, prepolymer isocyanates or "blocked isocyanates" are used when polyureas are prepared. Recent applications of this chemistry are reviewed in an article titled "Blocked Isocyanates in Coatings" by Mobay Chemical Corp., presented at "Water-Borne and Higher Solids Conference", Feb. 5-7, 1986, New Orleans, La. There are areas of commercial interest where specific products based on blocked polyisocyanates exhibit possible uses, see "Journal of Coatings Technology," Vol. 58, No. 738, Jul. 1986, pp: 49-54.
The preparations and uses of prepolymers-derived from the polyol and diisocyanate reaction are exemplified in U.S. Pats. No. 4,617,349, 4,614,787, 4,611,043 4,490,254 and 4,605,504. In a related U.S. Pat. No. 4,609,718, an adduct of a polyoxyalkylene diamine having molecular weight of 2000 and diiocyanate at 1:2 molar ratio was used as a precursor for coating applications.
It would be a distinct advance in the art if a novel polyoxyalkylenediamine containing urea groups could be prepared wherein the hardness of such cured coatings was controllable. Such a technique needs to avoid gel formation. In addition it would be a desirable property of the diamine if it were colorless, and the process of preparing these amines could be carried out at low temperature and without a catalyst. Uses of compositions with such desirable properties would be broad, especially in coating applications described in this application.